Electronic devices based on storage of electrons at an interface are well known. Devices containing interfaces formed by a silica (SiO.sub.2) layer disposed on a silicon (Si) substrate are presently in predominant use where the silica layer is provided by controlled oxidation of the silicon substrate. Examples of other substrates in addition to silicon include gallium arsenide (GaAs) and indium phosphide (InP). The charge carrier, i.e., electrons or holes, in such devices are stored at the interfaces and it is desirable to keep leakage current in such devices to a minimum in order to minimize loss of the charge. The electronic devices of silica disposed over a silicon substrate have low leakage current. Unfortunately, the present electronic devices of silica disposed over a diamond substrate have an undesirably high leakage current which drains the charge in such devices over a period of time.
Energy band gap is important especially in optical applications for the electronic devices. The width of the band gap is the lowest energy to which the device is responsive. This means that a device with a large or a wide band gap will be responsive to a limited energy range. Since band gap of diamond is about five times that of silicon, electronic devices with diamond substrates are responsive to a more limited energy range than electronic devices with silicon substrates. Specifically, electronic devices with diamond substrates don't respond to visible light whereas electronic devices with silicon substrate are responsive to visible light.
Diamond has many desirable properties which make it especially suitable for electronic, optical and medical applications. Diamond has an energy band gap of 5.5 ev and it generates a limited number of electrons when bombarded with alpha particles, which is indicative of high radiation resistance. Attempts have been made in the past to make semiconductor electronic devices with a diamond substrate and a thin layer of silica on the diamond substrate. Electronic devices having a diamond substrate with a layer of silica thereon have many desirable attributes including reduced leakage current and reduced response to visible light. However, electronic devices of a diamond substrate with a silica coating thereon have not proven to be feasible because of poor adhesion of the silica coating to the diamond substrate and the weak or fragile coating itself, as evidenced by the fact that the silica coating on the diamond substrate can be easily scratched with a tungsten probe.